Aluminum as a material is cheap because it is so abundant (it was once considered "rare"). However, plastic is easier to work with because it doesn't bend or crease as easily. My guess is that by switching the mid-range model to plastic Apple was able to free up resources to build more of the 5s. So even if producing plastic itself is more costly, it winds up being more cost effective in production.
11/17/13 at 9:53am